For a large social networking service that has millions, or in one case, billions of users, it is advantageous for marketers to present ads on webpages of the service to the users of the service. Additionally, when marketers pay for ads, it is desirable to be able to measure their return on investment by tracking and analyzing user actions associated with posted ads. Conversion tracking can be performed to determine which user actions, such as liking a page or sharing a post in the social networking website, redeeming a coupon, and buying a product, are associated with particular ads posted on webpages of the networking service.